In the electrical utilities industry, maintaining cable integrity may be critical. A loss of cable integrity, for example, a short circuit in a high voltage cable, may result in a crippling power outage or, even worse, a loss of life. One everyday task that may pose a great threat to cable integrity is the formation of electrical connections.
When a power cable is terminated, the termination may create an abrupt discontinuity in the electrical characteristics of the cable. The discontinuity may change the shape of the resulting electrical field electrical stress, which may increase the risk of the insulation breaking down.
Electrical stress concentrations in cable terminations can cause degradation of cable insulation. To address this problem, terminations are commonly provided with stress control elements (e.g., a stress cone or high-K layer). Two general classes of stress relief elements include high-K or capacitive type stress relief elements and geometric type stress relief elements. A high-K type stress relief element may be generally cylindrical and may rely primarily on material selection to manage the electrical field in the electrical stresses.
At medium voltages, such as 69 kV, a high-K type stress relief element may be implemented as two separate tubes that are layered. One tube may include a high-K material and may be installed to cover the entire portion of the termination and another tube that covers only a portion of the termination.
A geometric type stress relief element may rely on the geometry of its design and material type to manage the electrical field and electrical stresses. For example, geometric type stress relief elements may include a deflector portion that pushes electric stress in the outward direction. At lower voltages, such as 5 kV, the deflector may be relatively small and may be provided in cold shrink termination devices. However, in medium voltage cable terminations, such as 69 kV, the size of the deflector portion in a geometric type stress relief element may become too great for reasonable implantation in a cold shrink termination. As such, improved stress relief solutions are needed for power cables.